The present invention relates to an apparatus that is used in the automatic fixation of self-piercing fasteners of the stud type on a relatively thin metallic panel, by forcibly driving them onto the panel.
Every fastener of this type comprises a threaded or non-threaded stud, a flange-shaped head and a cylindrical lug continuing therefrom, with the head formed at one end of the stud. The lug pierces a metal plate or the like (see for example the Japanese Patent Publication No. 7-41357 corresponding to U.S. Pat. No. 4,729,163, or see Patent Laying-Open Gazette No. 7-167128 and Utility Model Gazette No. 58-135516).
In order to attach such stud type self-piercing fasteners to a metallic panel, a punch or plunger for driving them is used in combination with a caulking die. This die will receive each cylindrical lug driven through the panel and assists it to take an interlocking position. In detail, the annular wall of said lug will be deformed radially and outwardly within the die and along the back of the panel. Those fasteners successively advancing in between the punch and die facing one another should take precise position coaxial with them, before struck onto the panel. If such operations are to be carried out on a large scale, the feeding and subsequent positioning of fasteners have to done in an automatic manner.
The Patent Publication 7-41357 discloses a die set assembly for automatic installation of self-piercing fasteners of the stud type. This apparatus comprises a fastener feeding section such that the sequentially fed fasteners take their position perpendicular to the axis of the punching plunger, forming a horizontal row behind the plunger (see FIG. 15 in the Publication). Alternatively, that apparatus may comprise another type of the fastener feeding section such that the fasteners take their position substantially in parallel with the axis of the punching plunger, forming a vertical row (see FIG. 20 in the Publication).
The fasteners discharged horizontally from the feeding section of the former type will then transfer into and advance through a descent passage formed in that apparatus, merely due to gravitational force. Therefore, a problem has been encountered that they could not necessarily be supplied to the punching plunger section in a reliable manner, sometimes failing to become aligned with said plunger and the caulking die.
In another case of the apparatus employing the latter type feeding section, the fasteners discharged vertically and successively therefrom will then be driven sideways by a pusher into alignment with those punch and die, in a surer manner. A flexible tube for conveying a vertical row of the fasteners has a large radius of curvature and extends a considerable vertical distance. Thus, this apparatus is rendered so high as failing to suppress overall height of a pressing mold equipped with it. Depending on given xe2x80x98shut heightxe2x80x99 of the pressing mold, it often has been impossible to equip it with the fastener incorporation apparatus, particularly for the fasteners with long studs.
An object of the present invention made in view of such drawbacks is therefore to provide an improved apparatus for automatic fixation of self-piercing fasteners on a metal plate. The apparatus preferably comprises a fastener feeding section for conveying the fasteners in a continuous horizontal row. It is desirable that the feeding section is not only of a reduced overall height, but also the fasteners leaving the feeding section are surely transported towards a destination within the apparatus. The fasteners have to simultaneously be caused to take there a precisely aligned position, thereby rendering the apparatus extremely compact as a whole.
To achieve this object, the apparatus provided herein is constructed, as in the prior art apparatuses, for automatic fixation self-piercing fasteners each having a threaded or non-threaded stud, a flange-shaped head formed integral with one end of the stud and a cylindrical lug protruding from and coaxial with the head. It is important herein that the apparatus comprising a fastener feeding section, and a transportation mechanism for receiving the fasteners from the feeding section and transporting them to a punching station, is constructed as follows. The punching station will comprise a pressing punch, and a caulking die facing the pressing punch such that the fasteners are fed in between the pressing punch and the caulking die supporting a metallic panel so as to take their position coaxial with the punch and the die. The fasteners will then be struck with the punch onto the panel in a manner that the cylindrical lug does pierce the panel and an end rim of the lug is deformed with the die radially and outwardly to fixedly secure the fastener on the panel. More characteristically, the apparatus is such that the feeding section for conveying the fasteners in a continuous horizontal row makes it possible for each fastener to lie substantially perpendicular to an axis of the punch, with the cylindrical lug preceding the head integral with the stud of each fastener. Further, the transportation mechanism provide herein is capable of gripping the fasteners successively leaving the feeding section, then tilting them sideways one by one to stand upright and transporting them to the punching station where each of them is precisely aligned with the pressing punch one after another.
Preferably, both the feeding section and the transportation mechanism may be mounted on a punch block to which the pressing punch is secured to be movable up and down.
Also preferably and more typically, the transportation mechanism may comprise a tilting member, a translationally movable member, a pair of grip fingers and an actuator for the tilting and movable members. The tilting member may be held rotatingly on and by a transverse shaft that is horizontally fixed in the punch block so that this member can change its upright position to its laterally-turned position, or vice versa. The movable member may be connected to the tilting member in such a fashion as to make a translational motion towards and away from the tilting member. The grip fingers that are disposed on the movable member so as to move in unison therewith are however capable of passively opened and closed. By virtue of such a structural feature, the grip fingers will open to receive and firmly hold in position one fastener that has just been delivered from the feeding section and is still lying on its side while the tilting member is kept upright. As the tilting member is driven to take the laterally-turned position, the fastener gripped with the fingers will have its axis brought into parallel with the axis of the pressing punch. Subsequently, these axes will come into alignment with each other so as to make the fastener to take an exact position relative to said punch as the movable member is driven forward away from the tilting member.
A distal end of the pressing punch may have an aperture formed therein so as to fit on the stud as well as a retainer for temporarily keeping the stud in said aperture.
The apparatus may further comprise a stopper disposed in the vicinity of a downstream end of the feeding section. The next or succeeding fastener will engage the stopper so as not to unintentionally move ahead, until the tilting member having moved and is still moving for the preceding fastener restores its upright home position. Upon restoration of the home position by the members, an unlocking pawl disposed in either the tilting member or the movable member will free the stopper, so as to reliably feed and firmly grip the succeeding fastener in the next cycle.
It may also be preferable that the actuator for the tilting and movable members does comprise a guide groove consisting of an arcuate zone and a straight zone continuing therefrom, both the zones formed in the punch block. A pin or drive shaft may be secured on the movable member and slidingly fit in the guide groove, so as to be driven by principal and reciprocating parts of the actuator. Thus, the tilting and movable members will be forced to swing in unison and around the transverse shaft so long as the pin remains in the arcuate zone. Once the pin has entered the straight zone to gradually change its position therein, the movable member will be driven away from or towards the tilting member.